STEM CELLS IN LIVER GROWTH AND REGENERATION

拟议研究的长远目标是确定 不同肝细胞亚群对肝生长的贡献， 再生他们试图解决一个长期存在的争议， 肝干细胞是否存在， 损伤，可以产生能够分化成新 肝细胞（"兼性"干细胞）。这些研究是基于 新的转基因小鼠模型，其中肝毒性表达尿激酶- 型纤溶酶原激活剂通过白蛋白靶向肝细胞 增强子/启动子。由于方法论和范式 大鼠肝脏生长研究的重要性，这种转基因模型 将在这个物种中繁殖。在这些转基因动物中， 细胞，来源于肝细胞祖细胞， 转基因阵列，扩增并最终取代整个转基因- 表达薄壁组织。因此，白蛋白尿激酶动物的成年肝脏 是体细胞嵌合体肝细胞不含完整的转基因拷贝 因此它们和它们的后代不能表达转基因，而 剩余的肝细胞具有未重排的转基因。这些肝脏 动物经受预测激活干细胞谱系的条件 （以"卵圆细胞"增殖为代表）应显示转基因 如果非肝细胞前体（具有完整的转基因）可以 产生肝细胞。如果只有预先存在的肝细胞可以引起 新的肝细胞，转基因表达将不会被重新激活。因此，在本发明中， 该模型中的肝细胞谱系在遗传上是不同的;结论 关于细胞谱系潜力的问题可以使用稳定的标记物来解决 代替不太可靠标准如基因的形态或模式 表情这些研究进一步提出了卵圆细胞的特征 在白蛋白尿激酶动物中自发出现的群体， 确定该人群对额外肝损伤的反应， 确定消融肝脏辅助细胞对该反应的影响 (the Ito细胞），或卵圆细胞群的特定亚群（那些 表达甲胎蛋白）。

The long-term objective of the proposed studies is to identify the contributions of different liver cell subpopulations to hepatic growth and regeneration. They seek to resolve a longstanding controversy about whether liver stem cells exist that, under conditions of extreme hepatic injury, can give rise to progeny capable of differentiating into new hepatocytes ("facultative" stem cells). These studies are based upon a novel transgenic mouse model in which hepatotoxic expression of urokinase- type plasminogen activator is targeted to hepatocytes by the albumin enhancer/promoter. Because of the methodological and paradigmatic importance of the rat to studies of liver growth, this transgenic model will be reproduced in this species. In these transgenic animals, clones of cells, derived from progenitor hepatocytes that physically deleted the transgene array, expand and eventually replace the entire transgene- expressing parenchyma. Thus, the adult liver of albumin-urokinase animals is a somatic chimera hepatocytes do not contain an intact transgene copy and thus they and their progeny cannot express the transgene, whereas remaining liver cells possess an unrearranged transgene. Liver of these animals subjected to condiitons predicted to activate the stem cell lineage (represented by "oval cell" proliferation) should display transgene reactivation if non-hepatocytic precursors (with an intact transgene) can give rise to hepatocytes. If only preexisting hepatocytes can give rise to new hepatocytes, transgene expression will not be reactivated. Thus, hepatic cell lineages in this model are genetically distinct; conclusions regarding cell lineage potential can be addressed using a stable marker instead of less reliable criteria such as morphology or patterns of gene expression. These studies further propose to characterize the oval cell population that appears spontaneously in albumin-urokinase animals, determine how this population responds to additional hepatic injury, and identify the effect on this response of ablating an hepatic accessory cell (the Ito cell), or a particular subgroup of the oval cell population (those expressing alphafetoprotein).